You have to watch it over time, not hour by hour.

Block amounts are random and luck is a factor.  If the pool gets a string of bad luck and gets a lot of low value blocks, payout will be lower than average for that period. Just like it can be higher than average if there is really good luck and a long string of high value blocks are found.

IMHO from what i've seen.. except for that string of horrible luck that happened on fast-pool while dogepolis was actually functioning, fast-pool has actually had really good luck overall.